taohe

Move smart contracts implementing nestable resources on MoveVM blockchains

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回 TaoHe: Collection of nestable Move resources

TaoHe is a collection of nestable smart contract resources that can be used to create secure on-chain applications on MoveVM blockchains, such as Diem. Resources can be nested like a Russian doll (матрёшка), or Chinese boxes (套盒), the namesake of this project. 回 is used as the logo, since it depicts a box inside another box.

Tao is a simple Move resource that has been designed to be nested inside other taos. TaoHe is a collection of taos, and a special Root resource that can be used to store a resource directly into an account (taos themselves can be stored into resources only, for simplicity).

Example: You could place Diem tokens into a time locked tao, and place that inside an NFT tao, effectively creating a non-fungible time locked token.

Participate to TaoHe discussion on Diem Community.

Design

What taos are

Taos are meant to form disposable structures that contain a meaningful resource (such as Diem tokens). In order to access the resource in question, taos must be dismantled. A new tao can be created though, if so desired. Nesting taos inside each other can form complicated logics, such as time locked non-fungible tokens.

Why taos are small

Keeping code footprint per each tao in minimum is vital for safer code, and is simpler to audit. Keeping taos simple also shifts the code footprint to scripts, which are easier to develop and update than smart contracts.

Tao lifespan

Tao’s lifespan is divided into three separate phases, listed here chronologically:

What taos are not

Taos are not meant to replace specialized smart contract development for complicated applications, but can be used as part of one.

Building and developing

TaoHe is developed with Microsoft’s Visual Studio Code and the great Move Language plugin by Pontem Network, originally developed by damirka.

We use Dove build system 1.3.2 for building, package management, dependencies, formal verification and testing. After successful Dove installation, you can just run:

dove build

Jumpstart: dove run -v "immutable(_)" (replace immutable with any function residing in scripts/)

Formal verification

Every tao has formal verification specs embedded. You can run the formal verification by running:

dove prove

You’ll need boogie and z3 solver, which can be easily installed with Diem’s development setup script: ./scripts/dev_setup.sh -y. If you want to change the default paths, edit ./prover-env.toml.

Warning: Although every tao has formal verification specs, move-prover is still under development, and might have some limitations. Please see each source file for more information.

Using TaoHe for your projects

You can also add TaoHe as a dependency for your Dove based project by adding this line to your project’s Dove.toml:

dependencies = [{ git = "https://github.com/taoheorg/taohe", rev="c3b766a3a7e7ca05d9dbf68dfe9c5e6f6fd44131" }]

Warning: Due to signed commits, commit hash should be used, since it cannot be spoofed. After you know which TaoHe version you want to use, replace rev with your desired commit hash.

Known problems

Poor developer experience

DX is not good at the moment, since types must be known beforehand, and written in their full form, resulting in lengthy inscrutable lines of code. This could be solved by creating an intermediate Yaml based description language which could be used to generate transaction scripts and transaction script modules (a new Move feature).

Documentation

See doc/ for dove doc-gen generated documentation.

This repository is released under the Apache License 2.0, and is originally copyrighted to Solarius Intellectual Properties Ky (Forssa, Finland, EU). This project currently depends on diem-stdlib and move-stdlib. No warranty or fitness for a particular purpose provided, as stipulated in the License.

Trusted source

Smart contracts are mission critical and as such should always originate from trusted sources. That’s why every commit on master is signed with Ville’s GPG key. Upstream repository is here and the official webpage is at www.taohe.org.